1. Field of the Invention
The present invention relates to a reeding detection apparatus detecting existence of reeding provided to a peripheral surface. Specifically, the present invention relates to a coin sorting apparatus sorting a coin into a true coin or a false coin, based on existence of reeding provided to a peripheral surface, and more specifically, to a coin sorting apparatus sorting out a coin having reeding on a peripheral surface and having non-magnetic and strong conductive properties. Specifically, the present invention relates to a coin sorting apparatus sorting out a U.S. 25 cent coin. In the present specification, the term “coin” includes hard currencies, tokens, medals, and the like, and includes circular and polygonal shapes.
2. Description of Related Art
A U.S. 25 cent coin has a diameter of 24.26 mm and reeding on a peripheral surface. The coin has a commonly-called clad structure, in which a flat circular copper plate is coated with brass. Thus, the U.S. 25 cent coin has physically non-magnetic and strong conductive properties. An optical method is employed in conventional art in an apparatus detecting reeding on the peripheral surface (refer to Related Art 1).                [Related Art 1] Japanese Patent Laid-open Publication No. H9-167270 (FIGS. 1 and 2)        [Related Art 2] Japanese Patent Laid-open Publication No. H8-235407 (FIG. 3)        [Related Art 3] Japanese Patent Laid-open Publication No. H8-022564 (FIG. 1)        
The conventional art employs an optical method, which requires a light projector/receiver, a comparison circuit, a computation circuit, and the like, thus leading to a high cost. Meanwhile, a credit card reading apparatus is widely used as a billing apparatus in the U.S., and a payment is generally made with a credit card. In case in which a user owns no credit card, a billing apparatus in an automated machine needs to be equipped with a billing apparatus for coins. In this case, the billing apparatus for coins is an ancillary billing apparatus, and thus the apparatus needs to be provided at a low cost, and yet at the same time, the apparatus should not accept a false coin. A coin sorting apparatus having an electric sensor is required to sort out a plurality of denominations, thus increasing cost and being unable to meet the low cost requirement. A mechanical coin sorting apparatus is preferable as a low cost billing apparatus, but the apparatus is able to sort out a single denomination alone. It is thus preferable that a mechanical coin sorting apparatus for 25 cent coins be selected in the U.S., as a mechanical coin sorting apparatus. A conventional mechanical coin sorting apparatus generally identifies mainly a diameter of coins at a high accuracy, and identifies a material and thickness at a low accuracy. The conventional mechanical coin sorting apparatus thus has a problem of accepting false coins formed of a low cost material and having the same diameter. It is then considered to detect reeding on peripheral surfaces of 25 cent coins. An photoelectric reeding detection apparatus is expensive, however, as described above, and thus the apparatus cannot be employed.